Field of the Invention
The present invention relates to an optical information recording and reproducing apparatus and an optical information recording and reproducing method both of which are used for recording and reproducing information by converging a laser beam so as to form a minute spot on an information recording medium. More particularly, the present invention relates to an optical information recording and reproducing apparatus and an optical information recording and reproducing method both of which can be compatibly used for recording and reproducing information for a plurality of different types of information recording media each having inherent spot size of laser beam to be converged, by using a laser beam of a fixed wavelength.